1. Field of the Invention
The invention relates to a level shifter, and more particularly to a level shifter capable of dealing with extreme input signal level voltage drops and compensating for device PVT variation.
2. Description of the Related Art
A level shifter is used to convert an input signal defined relative to a first reference voltage into an output signal defined relative to a second reference voltage. A typical level shifter receives the input signal via a pair of transistors. However, when extreme input signal level voltage drops occur, the capability of driving the transistors becomes weak and circuit latency increases. Moreover, the extreme voltage drop may further cause undesired duty cycle variation of the output signal, or even cause the level shifter to function fail because the input transistor cannot be turned on by the extreme low input signal.
To solve the problems, a novel level shifter design capable of dealing with extreme input signal level voltage drops and further compensating for device PVT variation is desired.